Cellulose solution



Patented Fa. 16,1937 2,070,999

CELLULO SE SOLUTION Donald H. Powers, Moorestown, N. J and Louis H.Bock, Bristol, Pa., assignors to Riihm & Haas Company, Philadelphia, Pa.

No Drawing. Application February 8, 1934, Serial 8 Claims (01. 260-100)This invention relates to improvements in the peratures and theirsolvent action is greater at preparation of aqueous solutions ordispersions higher temperatures. This eifect is the opposite ofcellulose. In particular it relates to solutions of that found byLilienfeld because the bases or dispersions of alpha cellulose or otherslightly described by him were more effective solvents at disintegratedcellulose which is not dissolved or lower temperatures.

at best is only swollen at ordinary or elevated It is well known thatwhen cellulose is disintemperatures by concentrated alkaline solutions.tegrated or degraded its mechanical strength is This application is acontinuation in-part of impaired. This applies also to the regeneratedour copending application Ser. No. 676,530 filed material in the form ofsheets or fibers and 10 June 19, 1933, Patent No. 2,009,015 granted Julyhence it is advantageous to obtain a regenerated 10 23, 1935. cellulosefrom a material which has been disin- It is an object of this inventionto provide a tegrated or degraded as little as possible. The method forthe preparation of filterable solutions quaternary ammonium bases ofthis invention of cellulose which contain high percentage of are allcapable of dissolving alpha cellulose or cellulose and which do notdeteriorate on storing very slightly degraded cellulose under the con-15 nor on exposure to light. It is a further object ditions given andthe cellulosic material recovto prepare such solutions at hightemperatures. ered from such solutions by dilution or acidifi- Otherobjects will appear hereinafter. cation are superior in mechanicalstrength. It has been known for some time that certain Forms ofcellulose which have been degraded organic bases have a swelling actionon alpha least are alpha cellulose and sulfite wood pulp. cellulose butin order to prepare filterable solu- These materials give the bestresults on regentions of alpha cellulose the treatment required erationand therefore it is decidedly advantageous is much more drastic. toprepare highly concentrated solutions of these Lilienfeld (U. S. P.1,771,462), dissolved celforms of cellulose. lulose in solutions oftetramethyl, tetraethyl and Such solutions may be prepared by using a 25trimethylphenyl ammonium hydroxides, but in suitable quaternary ammoniumbase and treatorder to obtain complete solution, the cellulose ing thecellulose at comparatively high temperahad to be disintegrated to acertain degree or tures. the temperature kept at room temperature or be-Among the quaternary ammonium hydroxides s low. In case undisintegratedor slightly disinwhich we have found to be effective as cellulosetegrated cellulose were used, it would dissolve in solvents at hightemperatures are the following: 1 33 3 g si fif only, at temperaturesTrimethylbenzyl ammonium hydroxide We have found, however, thatsolutions of Trimethylpropyl ammolnum hydrmflde or tetramethyl andtetraethyl ammonium hydrox- Tnmethylbutyl ammomum hydroxlde w) ides donot dissolve more than one or two r- Trimethylamyl ammonium hydroxidecent of undisintegmted cellulo pe 'Trimethylhexyl ammonium hydroxide seat room temperature or merely act as swelling agents in a Tnmethylheptylammomum hydroxlde Trimethylallyl ammonium hydroxide manner similar tosodium or potassium hydroxide. 40 The same is true if these materialsare used at g ('8methy'1a11y1 ammomum hydrox- 40 elevated temperatures.

W Triethylbenzyl ammonium hydroxide e have now found that certam of thequater Dimethyldibenzyl ammonium hydroxide any ammomum bases w lldissolve cellulose at Dimethylamylbenzyl ammonium hydroxide ghtemperatures and W111 yield clear, filterable Triam lmethyl ammoniumhydroxide solutions of high cellulose content. Such basesTributiilmethyl a onium hydroxide 45 must,, of course, be stable at thetemperatures employed which may be as high as '150" C. For gmphenylethyl) ammomum hydroxi gg i gzggi ggg gfifi'zgg i g .basesDimethylphenylbenzyl ammonium hydroxide ight are suitableimethyltolylbenzyl ammonium hydroxide and in partmular those whichcontain at least Dieth 1 hen lbenz 1 am 0 h d 50 one benzyl group oralkyl group having three or y p y y m mum y roxl more carbon atoms.Suchouaternary amnio- The methyl groups in the above quaternary niumbases are unique in their action on celbases may be replaced by otheralkyl groups such lulose because of the fact that they are able to asthe propyLhexyl etc., and the benzyl groups dissolve undisintegratedcellulose at elevated temby the alkylated or similar substituted benzyl55 groups. The resulting compounds will be effective solvents forcellulose at elevated temperatures.

These bases have a range of concentration in aqueous solution withinwhich they are effective as solvents for cellulose and outside of whichthey cause gelatinization without forming filterable solutions. Forexample 2.6 normal trimethylpropyl ammonium hydroxide when heated withcotton linters for thirty minutes at 70 C. causes substantially completedissolving of the linters and the'solution may contain as much as 15% ofcellulose. If, however, the concentration of this base is only 1.5normal the fibres swell rapidly and finally gelatinize yielding asmooth, viscous and substantially clear paste. On filtration through acoarse medium such as spun glass, the filtrate contains little if anydissolved cellulose. Furthermore, if the solution of the trimethylpropylammonium hydroxide is about 3.2 normal the fibers will only gelatinizebut will not dissolve. The other bases show similar properties but theexact range of normality for the difierent bases varies somewhat fromthe above figures.

In the case of sonic bases, such, for example, astrimethylbenzylammonium hydroxide, their solvent action definitelyincreases up to a certain, normality, but increasing the normality ofthese bases beyond this point may not substantially decrease theirsolvent action.

While bases containing a phenyl group, such as the last four listedabove, have a limited solvent action at temperatures up to 40-50" C.they are of little practical value due to their extreme instability onheating.

Solutions of undisintegrated or only slightly disintegrated cellulosecontaining as much as 18 to 20% of cellulose may be made by means of theaqueous solutions of the quaternary ammonium bases when theconcentration of the latter lies within the proper range, viz. betweenabout 25% and 50%. The temperatures employed in making such solutionslie between about 50 and 150 C. Only those bases can be used which arestable at these temperatures because if they decompose under the actionof heat their solvent power is naturally lost.

Solutions made in accordance with the present invention may be dilutedto any desired cellulose content by the addition of solutions ofcaustic, ammonia or the quaternary bases. For this purpose solutionscontaining tour to eight percent;

of caustic or five to ten percent of ammonia or quaternary base aresuitable. In diluting such solutions with caustic or ammonia theconcentration of the quaternary ammonium base can be reduced to belowthe value required for the initial dissolving of the cellulose, withoutcausing precipitation. This is of importance because of the fact thatfor making a solution containing say five to eight percent of cellulose,less of the expensive quaternary base is required than if the solutionof cellulose were made up directly to that particular cellulose content.A solution of the quaternary ammonium base and caustic having the sameconcentration with respect to these materials as the diluted solutionmentioned above would have only a gelatinizing or swelling effect oncellulose and would not dissolve it.

In the foregoing, reference has been made particularly to alphacellulose or other slightly disintegrated cellulose. Since these are themost difficult to dissolve it is obvious that those types which aredegraded to a greater extent will be dissolved more easily by solutionsof the quaterheavy precipitate of cellulose.

-dibenzyl ammonium hydroxide.

nary ammonium bases. The following kinds of cellulose are usually atleast as easily dissolved as cotton 1inters:-

(1) Bleached sulfite or sulfate cellulose.

(2) Bleached cotton or cotton linters.

(3) Mechanical wood pulp.

(4) Cellulose oxidation products obtained from cellulose or cellulosecontaining bodies.

(5) Cellulose products obtained by treating cellulose containingmaterials with alkali of varying strengths with or without pressure.

(6) Regenerated cellulose such as viscose rayon, cuprammonium rayon,denitrated cellulose nitrate, or saponified cellulose acetate orformate' Any regenerated cellulose products precipitated from solutionor dispersion in sulphuric acid, phosphoric acid, zinc chloride, calciumthiocyanate solutions, or the like.

('7) Cellulose esters or ethers.

(8) Any form of hydrated cellulose or hydrocellulose.

The solutions thus prepared may be used for the manufacture of sheets orfibers of cellulose by passing the solution through a suitable orificeinto a strongly acid, neutral or alkaline solution. They may also beused for coating other fabrics with a layer of cellulose and in thisinstance the adhesion between the deposited cellulose and the underlyingfabric is unusually strong because of the solvent or swelling action ofthe solution on the cellulose of the fabric.

The invention may be practiced according to the following examples:-

1. One hundred fifty parts of cotton linters were stirred into 850 partsof 2.3 normal aqueous trimethylbenzylammonium hydroxide. This paste wasworked in 2. Werner and Pfieiderer nuxer. Steam was run into the jacketof the mixer until the temperature of the paste was approximately 70 C.The mix was worked for one hour at this temperature and formed a smooth,viscous paste. Mixing is continued until the cellulose is entirelydissolved. Then an equal volume of one normal sodium hydroxide solutionwas slowly added to the paste, lowering the viscosity considerably. Thisdiluted material, on acidification, or dilution with water gives a Itmay be precipitated in acid to form sheets or run thru an orifice toform synthetic fibers.

2. Ten parts of purified sulfite cellulose are mixed with 90 parts of2.8 normal aqueous trimethylamylammonium hydroxide. The mixture waswarmed in a jacketed kettle to 75 C. and gently stirred. At the end ofan hour a viscous paste was obtained, free from lumps and undissolvedcellulose. This paste may be used for coatings or diluted with normalsodium hydroxide solution to give less concentrated solutions.

3. Thirty parts of rayon waste were mixed with 200 parts of 2.0 normalaqueous dimethyl- The mixture was warmed in a jacketed kettle to C. andstirred until a smooth viscous paste was obtained. Heavy cotton duck wascoated with this paste and run immediateiy into acid, dried andcalendered. The resulting fabric had a very high luster and retained itsoriginal flexibility.

4. Sixteen parts of ground purified wood pulp were mixed with parts of2.2 normal aqueous trimethylbenzylammonium hydroxide. The mixture wasvigorously and rapidly heated to a temperature of (1., held at thistemperature for 10 minutes and rapidly cooled. The smooth solutionresulting was diluted at '70 to.- C. with 6% sodium hydroxide to acellulose content of 4%.

5. Six parts of cotton linters were stirred into parts of 2.0 normalaqueous tributylmethyl ammonium hydroxide at 50 C. The mixture wasallowed to stand for several hours and stirred for 30 minutes. Theresulting paste was precipitated in the form of fibers by forcing thrufine orifices into strong solution of sulfuric acid.

The foregoing examples are given by way of illustration only and are notintended to limit the invention as to concentrations, materials or otherconditions since the invention may be otherwise practiced within thescope of the following claims.

We claim:

1. The process of preparing cellulose solutions which comprises treatinga cellulosic body with an aqueous solution of a quaternary ammoniumhydroxide of the general formula N-OH R1 in which R, R1 and R2 representalkyl hydrocarbon groups and R3 represents an aralkyl radical or analkyl hydrocarbon group containing at least three carbon atoms.

2. The process of preparing cellulose solutions which comprises treatingundisintegrated cellulose with an aqueous solution of a quaternaryammonium hydroxide of the general formula N-OH R:

in which R, R1 and R2 represent alkyl hydrocarbon groups and R3represents an aralkyl radical or an alkyl hydrocarbon group containingat least three carbon atoms and thereafter diluting the solution with afour to eight percent. solution of an alkali metal hydroxide.

4. The process of preparing cellulose solutions which comprises treatingundisintegrated cellulose with an aqueous solution of a quaternary.ammonium hydroxide of the general formula ternary ammonium hydroxide ofthe general formula NOH a in which R, R1 and R2 represent alkylhydrocarbon groups and R3 represents an aralkyl radical or an alkylhydrocarbon group containing at least three carbon atoms.

6. A solution containing undisintegrated cellulose and a quaternaryammonium hydroxide of the general formula N-OH Ra R3 in which R, R1 andR2 represent alkyl hydrocarbon groups and R3 represents an aralkylradical 'or an alkyl hydrocarbon group containing at least three carbonatoms. 1

'7. The process of preparing cellulose solutions which comprisestreating a cellulosic body with an aqueous solution of a quaternaryammonium hydroxide of the general formula N-OH a in which R, R1 and R2represent alkyl hydrocarbon groups and R3 represents an alkylhydrocarbon group containing at least three carbon atoms. 8. The processof preparing cellulose solutions which comprises treatingundisintegrated cellulose with an aqueous solution of trimethylpropylammonium hydroxide.

DONALD H. POWERS.

LOUIS H. BOCK.

